Add: RetrieveAndExtend to session manager

Merged Akshay Bharambe requested to merge ab_Add_SMGetExt into devbranch

Add session sliding support to the session manager. Moved from SLS to v2 so that users can use this functionality from BL.

Closes https://corelab.mkcl.org/MKCLOS/coreosv3/corestudio/issues/446

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